Multiple Charging Sources to the Same Battery Bank

[estarzinger]

John,

Nick is more expert than me, but my understanding is that:

(1) if you are in acceptance and at 14.2 (or 14.6 in my case) then the batteries are already taking as many amps as they can (more amps would raise the voltage and cook them) and it's not just acceptable but desired that additional amps get diverted.

(2) if the voltage has not gotten up to 14.2 (or 14.6) then all sources and all regulators should be pumping out their maximum amps to the bank. If the voltage is below 14.2 and they are not pumping out maximum amps then their regulators are set wrong (or more likely there is a big voltage drop somewhere in the wiring).

[s/v Jedi]

John,

Thanks for the kind words ;-)

You have a very luxurious problem: too much power. My advise is to buy some BIG LCD screens for watching movies etc. ;-)

But let's see: solar and wind and during acceptance phase the wind gen output isn't used anymore. This is not a problem. During acceptance phase, the charge current will come down quickly, meaning you have more charge current available than the batteries can accept. I agree it's a shame to waste it, hence the big LCD screens. Or, dump the excess into the electrical element of the water heater for free hot water.

I have a much better solution still: sell the wind generator. You solar array is the bigger power source and it's maintenance free, without moving parts and other mechanical trouble.

ciao!
Nick.

[ka4wja]

Originally Posted by s/v Jedi

I have a much better solution still: sell the wind generator.

Nick,
Sorry about the confusion.....
I do NOT own a wind gen......and probably never will

I've got 520 watts of solar....not as much as you've got ....but I'm only a 47' sloop.....
And with my improved frig / freezer insulation of a few years ago, as well as use of Sensi-Bulbs inside and OGM LED Tri-Color at the masthead, as long as the sun shines every 3rd day, I'm mostly energy independent...(depends on how much the autopilot is drawing vs. how much sun I have.....)

But, I have worked on a few wind gens....and I read stories about those with both wind and solar having troubles with their controllers "fighting" each other....

Anyway, great discussion....



Sunny skies...

John

[s/v Jedi]

Originally Posted by ka4wja

I do NOT own a wind gen......and probably never will

But, I have worked on a few wind gens....and I read stories about those with both wind and solar having troubles with their controllers "fighting" each other....

Ah, very smart, we are of the same idea here ;-)

Much trouble with this is caused by cruisers that just buy and connect things without knowing what they are doing. WindGen's are not very smart and I see them as a power source only suited for bulk phase charging or even direct consumption before the power output is even used for charging. So, they are good if your batteries are never full. Solar is always better if you have room for the panels.

ciao!
Nick.

[ka4wja]

Nick,
Yes, great minds think alike....

Seriously, though, I do have a towed-water-generator which I deploy on long passages when needed.....typically only when cloudy skies plague me for a few days....
This has no controller, just a diode pack, and a breaker to disconnect it from the batteries.....
Works quite well....

Sunny skies and fair winds...

John

[schoonerdog]

OK, I'm learning a quite a bit, but I'm not sure if what I observe in 3 stage charger makes sense then. According to this thread, during bulk charging the charger (or chargers) will put out as many amps as it has available until the voltage reaches 14.5 volts. Then it backs off the charging amps and goes into a constant voltage mode, aiming at keeping the battery voltage around 13.2 volts or so. But here's the rub, I've looked at my solar chargers when they've been charging. They will charge for a few minutes and then back off for a few seconds in the bulk charge cycle and then go back to bulk charging. I'm assuming that they back off the charge cycle to determine the battery voltage minus the charge current. What is the reason for these pauses in the charge cycle? I would assume this function would be hindered by a second charging source keeping the battery voltage elevated.

[hellosailor]

'dog, the only way to know what any particular charger is doing, is to ask the maker. There are a number of different schemes in use.

For instance, a Delcotron classic alternator from the 70's puts out 14.4-14.3 volts *exactly* but it does so anywhere from something like 100-20,000 times per second. It goes "zap" and then it sense voltage, goes zap again if the voltage is below 14.3, stops when it sees 14.4.

Your charger is probably switching modes a bit slower than that, using the charging leads themselves instead of a dedicated sensing lead, and giving itself a moment to settle float or ignore transients or do some averaging at the same time.

Some makers are very paranoid about competitors and won't discuss what their boxes do. Most appreciate questions from a customer & will answer them though.

[s/v Jedi]

Schoonerdog,

What brand/type controller do you have? Do you have to program it in any way? (battery type, total Ah capacity etc.?). I don't like that backing off algorithm because you loose power while it is doing that, and the only voltage the controller should check is if that 14.4V is reached yet. I think that maybe something is overheating in your controller and it backs off because of that. Anyway, it's wrong. Bulk charge is old tech, it used to be the only phase before the smart-chargers came around.

Also, after bulk phase comes absorption. The voltage is held at that 14.4, not the 13.3 level yet. When you see 13.2 it's in the 3rd phase: float. Some (advanced) chargers/controllers have special features with more voltage levels during absorption (battery saving mode etc.), and an adaptive algorithm for the total time in absorption phase before switching to float. Some even have a 4th phase: storage.

For interference with radio's, fridge compressors etc. those high frequency PWM chargers/controllers are a negative. See Pulse-width modulation - Wikipedia, the free encyclopedia for a full description. You will see why it is an efficient method for varying the charge current but also why it caused EM interference plus noise on the DC system.

So, let me describe the best charger/controller for a cruiser:

• if powered from AC source: usable for any voltage and any frequency around the world
• if powered from solar array: support at least 150V VOC (array open output voltage)
• output current at 10-20% of total Ah capacity (100-200A charger for 1000Ah bank)
• DC output filtered so no or very low ripple. This means radio's can be used during charging without hums etc.
• at least 3 phases: bulk, absorption and float
• absorption and float voltages configurable
• absorption time adaptive AND fixed/configurable (user selectable)
• for adaptive absorption algorithm, the controller tries to figure out if the battery is full enough to switch to float. The best way is that it monitors the charge-current and it has to know the total Ah capacity of the bank charged to make that determination. All high quality chargers do it this way.
• The unit periodically switches back from float to absorption to prevent stratification and build-up of sulfate crystals on the plates.

ciao!
Nick.

[goboatingnow]

I'm assuming that they back off the charge cycle to determine the battery voltage minus the charge current.

no in practice the terminal voltage of a lead-acid cell during charing is only vaguely related to its stage of charge, what you are describing is a PWM charger, which some companies use, but more modern designs use better back end switching and do away with the pulse charging concept.

[hellosailor]

"but more modern designs...do away with the pulse charging concept. "

Although I have it from several sources who get paid very nicely to do battery engineering--including one of the top battery manufacturers in the US--that pulse charging, as in pulse width modulation, is the best way to charge and that it charges faster and deeper than a conventional "pure" DC charge because it doesn't stress (cook & bubble) the electrolyte the way that pure DC charging does.

The way they see it, there's PWM, and then there's dinosaurs. Everything else is--as usual--just a matter of whether the particular charger and charging logic is well engineered and executed, or a POS.

[s/v Jedi]

HelloSailor,

If I ever heard anecdotal evidence, this is it ;-)

I don't agree with it and would love to have a talk with these people. I think that they are talking about charge controllers like used for solar or wind generator, not about a battery charger that is powered by AC from shore power or genset. Those are now being replaced by MPPT so it's the museum for PWM in that arena.

There's more ways not to "cook" a battery but it is needed to know the temperature of the battery. A PWM charger can lower the duty cycle to provide some relief while a pure DC charger can lower the current. Result is the same.

In the end, it is the battery manufacturers to define the proper charging algorithm for their batteries and they all describe non-PWM technology. Also, none of the top chargers use PWM.

cheers,
Nick.

[bill good]

I've just about finished my solar installation & it is doing the job.I am using 2 X 200W 40v panels normally used on house installations. (80v@5A into the MX60). When the Mastervolt charger (20+20A bridged) feeds from either gen or shore power & the batteries are at float (13.8V) the MX60 shows "Batt Full". No problems so far with this system. I am seeing up to 20A into the battery with the panels level & weather just entering spring. (calculations were based on 50% ie 200w from 400w) At this stage the battery has not been below 11.9V over night on solar only. The engine alternators automatically feeds a common supply Bus with solid state relays to allow the solar to charge the house battery without any power being used by the boats systems.
The MX60 has "aux" function which allows a relay to switch at a preset Voltage. The use of relays could make your system automatic. 30A relays should be amply.

Regards Bill

[btrayfors]

Originally Posted by s/v Jedi

In the end, it is the battery manufacturers to define the proper charging algorithm for their batteries and they all describe non-PWM technology. Also, none of the top chargers use PWM.

cheers,
Nick.

Iota battery chargers -- one of the top and largest companies in the field -- uses PWM technology. And, in practice they seem to work better than pure DC chargers, including the high end ones like the Victron MultiPlus.

I have had 2 Iota chargers for 5 years and a MultiPlus for the same time, maintaining different banks of Trojan batteries. I have installed several others. I have had several talks with different Iota engineers, who confirm the design and the benefits of PWM technology in their chargers. Additionally, and anecdotally, Ford engineers investigating battery-charging techniques tout pulse charging as the very best way to charge a battery...fast and fully.

What I haven't yet seen, and would love to, are scientific reports describing side-by-side comparisons of PWM vs. pure DC charging with flooded batteries. My own experience tells me every day that PWM works very well, but like you I'd like to see some scientific research.

By the way, the Iota chargers are VERY RFI quiet. That's one of their benefits: they can be used right next to HF equipment and most of the time you can't hear them at all. Only time you can is when they're working very hard on a deeply discharged battery, and even then the RFI level is very low and tolerable.

Bill

[George Wade]

Originally Posted by s/v Jedi

Schoonerdog,

What brand/type controller do you have? Do you have to program it in any way? (battery type, total Ah capacity etc.?). I don't like that backing off algorithm because you loose power while it is doing that, and the only voltage the controller should check is if that 14.4V is reached yet......

• The unit periodically switches back from float to absorption to prevent stratification and build-up of sulfate crystals on the plates.

ciao!
Nick.

There is AccelRate Charging Of Vancouver, who put out a reverse pulse (every AC cycle?)
Q. How does AccelRate’s “high-speed” charger technology work?
A. AccelRate utilizes a charge/discharge algorithm that prevents build-up of the battery’s internal resistance by reversing the current, which forces the denser electrolyte away from the plates, resulting in a more even distribution of ions over the battery’s entire plate surface. Therefore, a higher charging rate can be maintained and the battery can be charged faster than with a competitive charger and to a full state-of-charge.....

www.accelrate.com/home.aspxI have to do some homework before seeing if they accept multiple power inputs at the same time.

Sales: Hawker Powersource - LifeSpeed® 3000 Charger N America and similar outlets in Europe. www.hawkerpowersource.com/products/LifeSpeed.htm

[George Wade]

That's www.accelrate.com I have to do some homework before seeing if they accept multiple power inputs at the same time. (Corrected URL)